Determinants of the ultimate outcome of unoperated patients with ductus arteriosus (DA) are not clearly understood. Generally, the samller the DA, the smaller the left-to-right shunt, the lower the pulmonary artery (PA) pressure and PA resistance, and the longer the survival. Not all patients, however, with these favorable characteristics do well, and conversely, not all patients with a longstanding large DA and a large left-to-right shunt do poorly. The latter was the case in the patient described in this report. The patient described lived his entire life with elevated PA pressures as reflected by the fetal pattern of elastic laminae in the pulmonary trunk, and during his last 27 years, by measured near-systemic PA pressures. Reports of 23 unoperated patients over 40 years of age with ductus arteriosus studied at necropsy were also summarized in this report.